In some businesses, there is an advantage to utilizing a computer system that allows existing services to be easily increased in capacity and enables new services to be easily introduced. For example, an Internet Service Provider (ISP) may maintain a server farm that is routinely expanded as the ISP gains subscribers. Online software vendors also benefit from the ability to readily expand capacity or capability.
An approach that facilitates capacity expansion and capability extension is rack mounting. FIG. 1 illustrates a rack mounted system 10 in which separate housings 12 contain sub-systems. A rack 14 includes slides which receive the housings on the basis of a particular standard. The sub-systems may be computers, computer appliances, or other cooperative equipment. The appliances may perform tasks such as spam filtering, network packet routing, firewall functions, or other functions that are needed by a particular enterprise.
A known industry standard for rack mounting is to provide measurements in 1U, 2U, 3U and 4U heights. A 1U height is approximately 1.6 inches (40.64 millimeters). The computers and other equipment are stacked on top of each other at a co-location facility, as shown in FIG. 1. The space at the facility can be expensive, so that the organization provided by the system is significant to the enterprise.
Within the various sub-systems, it is desirable to use a standard operating system (OS) and standard personal computer motherboards. The advantage is that application software and circuit boards are readily available from many suppliers in the market, if they are to be employed with the standard OS and motherboard. Thus, it is not necessary to design custom hardware. Only custom application software is needed in order to properly perform the operations required by a particular enterprise.
A difficulty is to provide all of the input/output functions while using standard motherboards. A motherboard typically has one or two Ethernet ports and has the other standard ports for a computer system. Additional ports are often needed for an appliance or for networking equipment. To add the additional ports to the system, an expansion card may be used or a custom motherboard may be designed and built. The custom motherboard is expensive and takes time to test and manufacture. Consequently, the preference is to utilize an expansion card. However, commercially available expansion cards are typically designed for use within a standard desktop computer and are approximately 4 inches (101.6 millimeters) in height (PCI and derivatives). Because the slots of the motherboard are designed to place the expansion cards in a vertical position, the cards cannot be used in a standard 1U chassis. FIG. 2 shows an example of an Ethernet card 16 that includes a port 18 and circuitry 20 that enables signal exchanges between circuitry on a motherboard (not shown) and an external system. An edge connector 22 on the card is mated to a slot of the motherboard. A metal bracket 24 is fixed to the back wall of the housing in which the Ethernet card is connected. Currently, a standard for an input/output card having a vertical orientation and a back-wall accessibility has been set for 2U-compatible chassis, but the standard is limited to such applications.
Riser cards allow the use of a standard-sized expansion card with a motherboard housed within a 1U chassis or a 2U chassis. A riser card is described in U.S. Pat. No. 6,533,587 to Potter et al. The riser card mates with the slot connector of the motherboard and includes a slot connector that permits the expansion card to reside in an orientation parallel to the motherboard, rather than perpendicular to the motherboard. Two such slot connectors may face in opposite directions from the riser card, so that the riser card permits two expansion cards to be located within the chassis.
Riser cards limit the number of expansion cards which may be installed. Because the riser cards place the expansion card or cards parallel to the motherboard, an expansion card may extend over slot connectors on the motherboard, preventing these slot connectors from being used. In addition, reliability and quality may suffer as a result of the need for the extra components and the additional connections. The number of input/output ports (such as Ethernet ports) may be increased by providing a DUAL or QUAD Ethernet adapter card, but these cards are sometimes cost prohibitive, since they require special hardware to multiplex the single expansion slot into the multiple input/output ports.
While known techniques operate reasonably well for their intended purpose, further improvements are desired.